Understanding the effect of environmental factors on link quality for on-board communications

1. Understanding the effect of environmental factors on link quality for on-board communications Irene Chan, Albert Chung, Mahbub Hassan University of New South Wales Kun-chan Lan, Lavy Libman National ICT Australia (NICTA) VTC2005 fall

2. About NICTA • A national research institute funded by Australia Government • Our research staff includes • regular researchers • contributed staff • from major universities such as Australian National Univ., Univ. of Sydney, Univ. of Melbourn, New South Wales of Univ. • Our focus • Research, commercialization, education, collaboration VTC2005 fall

3. About NICTA • 5 research labs • located in Sydney, Canberra and Queensland • 14 Research programs • Empirical Software Engineering; • Interfaces, Machines, And Graphic Environments • Networks and Pervasive Computing. • Embedded, Real-Time, and Operating Systems • Formal Methods • Symbolic Machine Learning and Knowledge Acquisition • Statistical Machine Learning; • Systems Engineering and Complex Systems • Wireless Signal Processing • Logic and Computation; • Autonomous Systems and Sensing Technologies • Statistical Machine Learning. • Sensor Networks; • Network Information Processing.

4. Agenda • Motivation • Search of the environmental factors that can be utilized for outage prediction for on-board communication • Measurement results • Conclusion and future work VTC2005 fall

5. Mobile Network • Growing interest in providing broadband service for public transport passengers • Mobile Network • On-board LAN • Mobile Router (MR) • Standardized protocol (RFC3963): NEMO • Extension of MIPv6 VTC2005 fall

6. Mobile Router Data Server On-Board LAN Exciting on-board applications VoIP surveillance entertainment email VTC2005 fall

7. Products/services already appearing! Cisco mobile router

8. On the research side • IETF NEMO working group [2002] • Nautilus6 working group [Japan, 2003] • Network Mobility project [Korea, 2003] • WirelessCabin [Europe, 2002] • Network On Wheels (NOW) [Europe, 2005] • PATH project [Berkeley] • Diesel project [Umass, Amherst] VTC2005 fall

9. Outages outage outage

10. Outage prediction • Important problem for on-board communication • Can impact a large number of users • Mobility pattern of public transport vehicles are known in advance • Utilize this feature for outage prediction • Mobile Router records signal strength and available bandwidth information at different times and at different locations • Predict outage by analyzing recorded information VTC2005 fall

11. Effect of environmental factors • Various factors might affect quality of wireless signal • While physical factors like noise, multi-path will obviously affect the signal strength, • In practice, not easy to utilize them for outage prediction • Environmental factors such as location, weather, time of the day, crowdedness, vehicle velocity, etc. • easier to observe/obtain and use VTC2005 fall

12. Contribution of this work • We conducted wide-area measurements by recording GPRS signal in different locations and under a variety of conditions in Sydney metropolitan area • We found location is the most dominating environmental factor affecting signal quality • Some cellular operators might have done this • but their measurements are not public available VTC2005 fall

13. Agenda • Motivation • Measurement results • preliminary results on location, speed, humidity, people and tunnel • Conclusion and future work VTC2005 fall

14. Data collection • We recorded signal strength of Vodafone’s GPRS network under different conditions in a 6-month period • Measurements were taken on the link between the receiver and base station • GPS is used to record location and time of measurements • Traces in collected on train, bus, car and some chosen locations VTC2005 fall

15. location • Signal strength is strongly correlated with locations across different times of the day VTC2005 fall

16. Signal strength map • 3 bus routes • Good quality: green • Bad quality: red • Similar patterns across different times and different days VTC2005 fall

17. Speed • No significance in signal strength level • Larger variations at a lower speed • Hypothesis: other environmental factors have a better chance to affect the signal at the lower speed • More handoffs at a lower speed

18. Handoff sequences • Sequence of switching between different base stations exhibit certain predictability • Suggest the feasibility of deploying some resource reservation scheme for on-board network

19. Humidity • Rainy: 2 millimeters per hour • No significant difference • Rain attenuation has a stronger in higher frequency band such as microwave link • GPRS uses 900MHz/1.8G • Some base stations uses microwave links to connect to Mobile Service switching Center (MSC)

20. People • Crowded: • lunch time • Non-crowded • Eastern break • No significant differences • Larger variation for crowded scenario VTC2005 fall

21. Tunnel • Tunnel does not lead to continuous outages • Micro-cell around the platform VTC2005 fall

22. Distribution of signal strength level • Gaussian distributed VTC2005 fall

23. Throughput during the day • Similar patterns across different days • Lower throughput during the business hours and in the evening • Hypothesis: user behavior VTC2005 fall

24. Conclusion and future work • We conducted wide-area GPRS measurements under a variety of conditions in Sydney metropolitan area • We found location is a better predictor for outage prediction than other environmental factors • Use measurement results to design practical outage prediction algorithm for on-board communication VTC2005 fall